1. Technical Field
The present invention relates to a coil component, and more particularly, to a coil component having an electrostatic discharge (ESD) protecting function.
2. Description of the Related Art
In accordance with the development of a technology, electronic devices such as a portable phone, a home appliance, a personal computer (PC), a personal digital assistant (PDA), a liquid crystal display (LCD), and the like, have been changed from an analog scheme into a digital scheme and a speed of the electronic devices has increased due to an increase in an amount of processed data. Therefore, a universal serial bus (USB) 2.0, a USB 3.0, and a high-definition multimedia interface (HDMI) have been widely spread as high speed signal transmitting interfaces and have been used in many digital devices such as a personal computer and a digital high-definition television.
These high speed interfaces adopt a differential signal system transmitting differential signals (differential mode signals) using a pair of signal lines unlike a single-end transmitting system that has been generally used for a long period of time. However, the electronic devices that are digitized and have an increased speed are sensitive to a stimulus from the outside, such that distortion of signals due to high frequency noise has been often generated.
In order to remove this noise, a filter has been installed in the electronic device. Particularly, a common mode filter for removing common mode noise has been widely used in a high speed differential signal line, or the like. The common mode noise indicates noise generated in the differential signal line, and the common mode filter removes the common mode noise that may not be removed by an existing filter.
Meanwhile, since a recent high speed digital interface treats fine signals of which a transmission speed is high, an integrated circuit (IC) very sensitive to electrostatic discharge (hereinafter, referred to as “ESD”) generated at the time of connection and disconnection between different devices) should be used. Therefore, Patent Document (Korean Patent Laid-Open Publication No. 10-2010-0037000) discloses a common mode filter including an ESD protecting layer protecting an internal circuit from static electricity.
That is, referring to FIG. 3 of Patent Document, the common mode filter further includes an ESD protecting layer 12b disposed beneath a common mode filter layer 12a functioning as a filter, wherein the ESD protecting layer includes an ESD absorbing layer 30 functioning as an ESD protecting material. Therefore, an overvoltage signal due to the static electricity passes through gap electrodes 28 and 29 maintaining a predetermined gap from a lead conductor. As a result, spiral conductors 17 an 18 of the common mode filter layer are protected.
However, the common mode filter disclosed in Patent Document has a structure in which the ESD protecting layer 12b is stacked on a magnetic substrate 11a in order to simultaneously fire the magnetic substrate 11a made of high temperature sintering ferrite and the ESD absorbing layer 30 made of a high temperature sintering insulating inorganic material. Therefore, the ESD protecting layer 12b is disposed between the common mode filter layer 12a and the magnetic substrate 11a.
The ESD absorbing layer 30 of the ESD protecting layer 12b contains an insulating inorganic material that is non-magnetic and has a lower magnetic permeability and a high magnetic resistance. Due to the above-mentioned structure, a main magnetic flux loop generated in the common mode filter layer 12a and formed using the magnetic substrate 11a as a closed magnetic circuit is blocked and lost by the ESD protecting layer 12b between the common mode filter layer 12a and the magnetic substrate 11a.